Water availability and land subsidence in the Central Valley,California, USA     

Claudia C. Faunt  Michelle Sneed  Jon Traum  Justin T. Brandt 《Hydrogeology Journal》2016,24(3):675-684

The Central Valley in California (USA) covers about 52,000 km² and is one of the most productive agricultural regions in the world. This agriculture relies heavily on surface-water diversions and groundwater pumpage to meet irrigation water demand. Because the valley is semi-arid and surface-water availability varies substantially, agriculture relies heavily on local groundwater. In the southern two thirds of the valley, the San Joaquin Valley, historic and recent groundwater pumpage has caused significant and extensive drawdowns, aquifer-system compaction and subsidence. During recent drought periods (2007–2009 and 2012-present), groundwater pumping has increased owing to a combination of decreased surface-water availability and land-use changes. Declining groundwater levels, approaching or surpassing historical low levels, have caused accelerated and renewed compaction and subsidence that likely is mostly permanent. The subsidence has caused operational, maintenance, and construction-design problems for water-delivery and flood-control canals in the San Joaquin Valley. Planning for the effects of continued subsidence in the area is important for water agencies. As land use, managed aquifer recharge, and surface-water availability continue to vary, long-term groundwater-level and subsidence monitoring and modelling are critical to understanding the dynamics of historical and continued groundwater use resulting in additional water-level and groundwater storage declines, and associated subsidence. Modeling tools such as the Central Valley Hydrologic Model, can be used in the evaluation of management strategies to mitigate adverse impacts due to subsidence while also optimizing water availability. This knowledge will be critical for successful implementation of recent legislation aimed toward sustainable groundwater use.  相似文献   

A low resolution map of Europa from four occultations by Io     

James R. Vermilion  Roger N. Clark  Thomas F. Greene  Jon F. Seamans  William F. Yantis 《Icarus》1974,23(1):89-96

Analysis of three occultations of JII (Europa) by JI (Io) has resulted in a preliminary reflectivity map of JII for the hemisphere centered on longitude 324°, a measurement of 1483±20 km for the radius of JII, estimates of the event impact parameters, determination of the mid event times, and a visual geometric albedo, p_ν = 0.74, for JII. A fourth occultation light curve was used after derivation of the results to confirm their validity.  相似文献   

Standardization of bluefin tuna, Thunnus thynnus, catch per unit effort in the baitboat fishery of the Bay of Biscay (Eastern Atlantic)     

Rodriguez-Marin  E.; Arrizabalaga  H.; Ortiz  M.; Rodriguez-Cabello  C.; Moreno  G.; Kell  L.T. 《ICES Journal of Marine Science》2003,60(6):1216-1231

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The effect of area closures on the demersal fish community off the east coast of Iceland     

Jaworski  Andrzej; Solmundsson  Jon; Ragnarsson  Stefan Aki 《ICES Journal of Marine Science》2006,63(5):897-911

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Collapse of the fishery for Iceland scallop (Chlamys islandica) in Breidafjordur, West Iceland     

Jonasson  Jonas P.; Thorarinsdottir  Gudrun; Eiriksson  Hrafnkell; Solmundsson  Jon; Marteinsdottir  Gudrun 《ICES Journal of Marine Science》2007,64(2):298-308

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Analysis of juvenile North Atlantic albacore (Thunnus alalunga) catch per unit effort by surface gears in relation to environmental variables     

Goni  Nicolas; Arrizabalaga  Haritz 《ICES Journal of Marine Science》2005,62(7):1475-1482

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Surveillance and enforcement operations in the Costa Rican tuna fishery     

Luis Guillermo Lepiz  Jon G. Sutinen 《Marine Policy》1985,9(4):310-321

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Towards a new spatial perspective – Norwegian politics at the crossroads     

Jon P. Knudsen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(2):67-81

The purpose of the article is to investigate how the hegemony of traditional regional policy in Norway has been weakened in favour of policies of a new type, derived from the combined effect of climate concerns and a search for increased structural efficiency. This phenomenon is identified as an ‘eco-spatial’ turn that marks a new policy regime with changing agendas. The policy transition is analysed by drawing on existing scientific literature in the fields concerned, central policy documents, and relevant news articles. The results of the analysis substantiate that a decisive turn has taken place, with the period of transition between the two policy types identified as 1992–2015. This shift in policy orientation has important institutional and political consequences, including the move from a perspective of demographic and economic expansion in space to one of contraction and a subsequent creation of spatial scarcity. To conclude, the author questions whether the new policy position is viable, given the deep-rooted nature of regional cleavages within Norwegian society. However, the formal institutional ability to deal with the situation at the national level is in place, since national planning and regional policies have finally been gathered within the confines of one ministry.  相似文献   

Tracking hydrological responses of a thermokarst lake in the Old Crow Flats (Yukon Territory,Canada) to recent climate variability using aerial photographs and paleolimnological methods     

Lauren A. MacDonald  Kevin W. Turner  Ann M. Balasubramaniam  Brent B. Wolfe  Roland I. Hall  Jon N. Sweetman 《水文研究》2012,26(1):117-129

Recent studies using remote sensing analysis of lake‐rich thermokarst landscapes have documented evidence of declining lake surface area in response to recent warming. However, images alone cannot identify whether these declines are due to increasing frequency of lake drainage events associated with accelerated thermokarst activity or to increasing evaporation in response to longer ice‐free season duration. Here, we explore the potential of combining aerial photograph time series with paleolimnological analyses to track changes in hydrological conditions of a thermokarst lake in the Old Crow Flats (OCF), Canada, and to identify their causes. Images show that the water level in lake OCF 48 declined markedly sometime between 1972 and 2001. In a sediment core from OCF 48, complacent stratigraphic profiles of several physical, geochemical, and biological parameters from ～1874–1967 indicate hydro‐limnological conditions were relatively stable. From ～1967–1989, declines in organic matter content, organic carbon isotope values, and pigment concentrations are interpreted to reflect an increase in supply of minerogenic sediment, and subsequent decline in aquatic productivity, caused by increased thermo‐erosion of shoreline soils. Lake expansion was likely caused by increased summer rainfall, as recorded by increased cellulose‐inferred lake‐water oxygen isotope compositions. Stratigraphic trends defining the lake expansion phase terminated at ～1989, which likely marks the year when the lake drained. Above‐average precipitation during the previous year probably raised the lake level and promoted further thermo‐erosion of the shoreline soils that caused the lake to drain. These are meteorological conditions that have led to other recent lake‐drainage events in the OCF. Thus, the decline in lake level, evident in the aerial photograph from 2001, is unlikely to have been caused by evaporation, but rather is a remnant of a drainage event that took place more than a decade earlier. After drainage, the lake began to refill, and most paleolimnological parameters approach levels that are similar to those during the stable phase. These findings indicate that combined use of aerial images and paleolimnological methods offers much promise for identifying the hydrological consequences of recent climatic variations on thermokarst lakes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Re‐analysis of key evidence in the case for a hemispherically synchronous response to the Younger Dryas climatic event     

Helen Green  Jon Woodhead  John Hellstrom  Robyn Pickering  Russell Drysdale 《第四纪科学杂志》2013,28(1):8-12

A south‐east Australian speleothem stable isotope record displaying an apparent cooling synchronous with the northern hemisphere Younger Dryas climate event (12.9–11.7 ka) has significantly influenced scientific thinking on the climatic response of the southern hemisphere following the Last Glacial Maximum. This is one of very few records displaying such a response, and yet the cooling was inferred from substantial extrapolation between just three uranium‐series ages. Technological advances since then have produced major improvements in both the spatial resolution and the accuracy of uranium‐series geochronologies. Re‐analysis of this sample has yielded ages of 7.96 ± 0.36 to 7.69 ± 0.33 ka for the interval previously inferred to span the Younger Dryas, and reveals a substantial hiatus in deposition from 6.93 ± 0.64 to 1.83 ± 0.16 ka. These data not only refute the original evidence for an inter‐hemispheric synchroneity of the Younger Dryas but also reject any evidence for neoglacial conditions at 3 ka. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献